Photosensitive polysilazane composition, method of forming pattern therefrom, and method of burning coating film thereof

ABSTRACT

A finely patterned silica type ceramic film suitable as an inter-layer dielectric is formed in a short time by applying, onto a substrate, a positive working radiation sensitive polysilazane composition comprising a modified poly(sil sesquiazane) having a number average molecular weight of 100 to 100,000 and containing a basic constituent unit represented by the general formula: —[SiR 6 (NR 7 ) 1.5 ]— and other constituent units represented by the general formula: —[SiR 6   2 NR 7 ]— and/or —[SiR 6   3 (NR 7 ) 0.5 ]— (R 6  and R 7  independently represent a hydrogen atom, a C 1-3  alkyl group or a substituted or unsubstituted phenyl group) in a ratio of 0.1 to 100 mol-% to said basic constituent unit, a photo acid generator and preferably a water-soluble compound as a shape stabilizer, then patternwise exposing the resultant coating film, subjecting the exposed part of the coating film to moistening treatment, developing it with an aqueous alkali solution, wholly exposing the coating film to light and moistening treatment again, followed by burning treatment.

TECHNICAL FIELD

This invention relates to a method of forming a patterned polysilazanefilm by using a radiation sensitive polysilazane composition, a methodof forming a silica type ceramic film by burning a patterned radiationsensitive polysilazane coating film, and a radiation sensitivepolysilazane composition to be used preferably in these methods.

BACKGROUND ART

In various fields including manufacture of semiconductor devices andliquid crystal displays, positive or negative working photoresists havebeen used for fine processing or patterning. As such photoresists, thereare conventionally known a positive working radiation sensitivecomposition comprising a novolak resin and a quinone diazidephotosensitizer, a chemically amplified positive or negative workingradiation sensitive composition, and a negative working resist such as apolyvinyl cinnamate-based radiation sensitive composition, abisazide-rubber-based radiation sensitive composition, and aphotopolymerization type radiation sensitive composition, etc. In suchphotoresists, there are required various characteristics depending ontheir intended use. For example, in processing of semiconductor devices,there are required characteristics such as high sensitivity, highresolution and etching resistance.

On the other hand, various patterned films including an inter-layerdielectric have been used in semiconductor devices, liquid crystaldisplays, printed circuit substrates, etc. These patterned film isformed generally by applying film-forming organic or inorganic materialsor depositing these materials from a gaseous phase to form a coating andthen etching the coating through a patterned photoresist. If there isnecessity for forming a fine pattern by this etching, gaseous etching isgenerally used. However, the gaseous etching is problematic because anapparatus used is expensive and the rate of processing is low.

Further, in the production step of semiconductor devices or the like(e.g. a vapor deposition step of wire by CVD), the devices are exposedto high temperatures at higher than 400° C. Accordingly, when organicmaterials are used as an inter-layer dielectric in the devices exposedto such high temperatures, it can not be opposed satisfactorily inrespect of heat resistance. Because of this, the use of inorganicmaterials is desired as the materials such as an inter-layer dielectric.As the inorganic materials, silica type ceramic films are often used bythe reason why it has superior not only in heat resistance but also inabrasion resistance, corrosion resistance, insulating properties,transparency, etc.

Conventionally, such patterned silica type ceramic film is formedgenerally by etching of a ceramic film using a patterned photoresist asan etching mask, and is economically problematic. Accordingly, there isa demand for a method of forming a finely patterned inter-layerdielectric without using gaseous etching.

For this demand, a method of forming a ceramic film pattern is proposedwhich comprises applying a radiation sensitive polysilazane compositionto form a radiation sensitive polysilazane coating film, exposing anddeveloping the coating film to form a patterned polysilazane film,converting the patterned polysilazane film into a silica type ceramicfilm. For example, JP-A 5-88373 describes a method of forming a ceramicfilm pattern which comprises applying a polysilazane-containing coatingsolution onto a substrate to form a coating film thereon, patternwiseirradiating the coating film with UV rays in an oxidizing atmosphere tocure the portion exposed to UV rays, removing a portion not exposed toUV rays, and converting the patterned polysilazane film into a silicatype ceramic film. The polysilazane-containing coating solutiondescribed above can be regarded as a negative working photoresistbecause the exposed portion cures and remains after development.

On the other hand, fine processing of semiconductor devices or the likeis advancing. As a result, a positive working material, as a resist,with high resolution and high etching resistance such as oxygen plasmaresistance is desired. Further, when the patterned coating is used as aremaining inter-layer dielectric, it is desired that the coatingmaterials satisfy not only the aforementioned requirements for fineprocessing but also excellent properties such as high heat resistance,low dielectric constant and transparency required for the inter-layerdielectric. For these demands, the present inventors proposed a positiveworking radiation sensitive polysilazane composition comprising apolysilazane and a photo acid generator; a method of forming a patternedpolysilazane film which comprises applying said radiation sensitivepolysilazane composition to form a coating film, patternwise irradiatingthe coating film, dissolving and removing the irradiated part of thecoating film to form a patterned polysilazane film; and a method offorming a patterned insulating film which comprises leaving saidpatterned polysilazane film in the ambient atmosphere or burning thefilm thereby converting it into a silica type ceramic film in JapanesePatent Application No. Hei 11-283106 (JP-A 2000-181069).

In addition, the present inventors proposed a positive working radiationsensitive polysilazane composition having improved storage stability byuse of a modified poly(sil sesquiazane) in Japanese Patent ApplicationNo. Hei 12-108023.

In the method of using these positive working radiation sensitivepolysilazane compositions, an acid is formed in the light-exposedportion of the radiation sensitive polysilazane coating film. By theacid formed, Si—N linkages in the polysilazane are cleaved and thenreact with H₂O molecules to form silanol (Si—OH) linkages, wherebydecomposition of the polysilazane occurs. In these prior art techniques,however, the treatment method described specifically as a method ofdecomposing the polysilazane is a method of bringing the exposedradiation sensitive polysilazane film into contact with water.

These proposed positive working radiation sensitive polysilazanecompositions have higher, resolution than that of the negative workingradiation sensitive polysilazane compositions, but it is necessary toimprove the resolution in order to cope with fine patterning. Further,the light-exposed radiation sensitive polysilazane composition iscontacted with water to decompose the polysilazane. Possibly because thedecomposition of the polysilazane proceeds only in the vicinity of thesurface of the film of the radiation sensitive polysilazane composition,the coating film in the exposed portion is not sufficiently removedunder some decomposition conditions by subsequent development with anaqueous alkali solution, and development residues may remain on thepattern after development. In addition, there is another problem thatthe adhesion of the radiation sensitive polysilazane coating film to thesubstrate is not sufficient. Accordingly, a method of decomposing aradiation sensitive polysilazane film free of aforementioned problems isalso regarded. Further, when the radiation sensitive polysilazanecoating film is converted by burning into a silica type ceramic film,oxidation of the polysilazane does not sufficiently proceed by merelyheating the polysilazane coating film. As a consequence of this, theresultant silica type ceramic film has a large number of Si—N linkagesof polysilazane in the coating film, thus making it difficult to form afilm having a sufficiently low dielectric constant required for aninter-layer dielectric. There is a further problem that when a largenumber of Si—N linkages remain in the silica type ceramic film, the filmeasily absorbs moisture to form a film having unstable physicalproperties. Accordingly, when burning the radiation sensitivepolysilazane coating film, a method of burning a radiation sensitivepolysilazane coating film is also demanded, wherein the polysilazane inthe coating film can be converted easily and sufficiently into silicatype ceramic film and give a silica type ceramic film excellent incharacteristics such as dielectric constant and free of residual Si—Nlinkages in the film.

In view of these circumstances, an object of this invention is toprovide a method of forming a patterned polysilazane coating by use of aradiation sensitive polysilazane composition, wherein the polysilazanein the radiation sensitive polysilazane composition after exposure canbe decomposed in a short time to give a patterned polysilazane filmexcellent in adhesion to a substrate and free of development residues onthe pattern after development.

Further, an object of this invention is to provide a method of burning aradiation sensitive polysilazane coating film wherein oxidation of thepolysilazane sufficiently proceeds even by simple heating so that no orfew Si—N linkages exist in the film.

Further, an object of this invention is to provide a radiation sensitivepolysilazane composition, a method of forming a patterned radiationsensitive polysilazane coating, and a method of burning a radiationsensitive polysilazane coating film, wherein a silica type ceramic filmwith a low dielectric constant, excellent in heat resistance, abrasionresistance, corrosion resistance, insulating properties and transparencyand useful as an inter-layer dielectric can be formed.

Further, an object of this invention is to provide a radiation sensitivepolysilazane composition having high resolution.

The present inventors made extensive study for achieving these objects,and as a result, obtained the following knowledge. That is, when forminga patterned polysilazane film by use of a positive working radiationsensitive composition such as a radiation sensitive polysilazanecomposition comprising a polysilazane and a photo acid generator, thepolysilazane can be decomposed in a short time, and development residuesdo not remain on the pattern after development by contacting the exposedradiation sensitive polysilazane coating film with a watervapor-containing gas, that is, subjecting to moistening treatment; thedecomposition time can be further reduced by increasing the content ofwater vapor in the gas used or by heating the radiation sensitivepolysilazane coating film at the time of moistening treatment; thepartial pressure of water vapor in the atmosphere for moisteningtreatment can be further increased by relaxation of the conditions ofmoisture condensation on the surface of the film in heating the film,whereby the time required for decomposition of the polysilazane can befurther reduced; and the adhesion of the polysilazane coating film tothe substrate is also improved by heating during development.

Further, the present inventors found that when the radiation sensitivepolysilazane coating film is burned, conversion of the coating film intosilica type ceramic film can be conducted easily and sufficiently byexposing the coating film and subjecting the resultant film to themoistening treatment before burning, to give a silica type ceramic filmexcellent in properties and free of Si—N linkages therein.

Further, the present inventors found that resolution can be increased byadding a water-soluble compound as a shape stabilizer to the radiationsensitive composition comprising a specific modified poly(silsesquiazane) and a photo acid generator, and this radiation sensitivecomposition can form a finely patterned inter-layer dielectric excellentin dielectric constant, insulating properties and mechanical propertiesafter burning.

This invention is based on these findings.

DISCLOSURE OF THE INVENTION

This invention relates to a method of forming a polysilazane film, amethod of burning a radiation sensitive polysilazane coating film, and aradiation sensitive polysilazane composition which have the followingconstitution:

[1] A method of forming a patterned polysilazane film by exposing andthen developing a coating film of a radiation sensitive polysilazanecomposition, wherein the exposed radiation sensitive polysilazanecoating film is subjected to moistening treatment and then developed.

[2] The method of forming a patterned polysilazane film according toitem [1] above, wherein the radiation sensitive polysilazane coatingfilm is heated at the time of the moistening treatment.

[3] A method of burning a radiation sensitive polysilazane coating film,wherein the steps of exposing with light and moistening the radiationsensitive polysilazane coating film are provided as pretreatment stepsfor burning.

[4] The method of burning a radiation sensitive polysilazane coatingfilm according to item [3] above, wherein the radiation sensitivepolysilazane coating film has been patterned.

[5] The method of burning a radiation sensitive polysilazane coatingfilm according to item [3] above, wherein the radiation sensitivepolysilazane coating film is heated at the time of the moisteningtreatment.

[6] A radiation sensitive polysilazane composition comprising a modifiedpoly(sil sesquiazane) having a number average molecular weight of 100 to100,000 and containing a basic constituent unit represented by thegeneral formula: —[SiR⁶(NR⁷)_(1.5)]— and other constituent unitsrepresented by the general formula: —[SiR⁶ ₂NR⁷]— and/or —[SiR⁶₃(NR⁷)_(0.5)]— (in the aforementioned formulae, R⁶ independentlyrepresents a C₁₋₃ alkyl group or a substituted or unsubstituted phenylgroup and R⁷independently represents a hydrogen atom, a C₁₋₃ alkyl groupor a substituted or unsubstituted phenyl group) in a ratio of 0.1 to 100mol-% to said basic constituent unit, a photo acid generator, and awater-soluble compound as a shape stabilizer.

[7] The radiation sensitive polysilazane composition according to item[6] above, wherein the photo acid generator is ones selected from thegroup consisting of a sulfoxime type compound and a triazine typecompound.

[8] The radiation sensitive polysilazane composition according to item[6] or [7] above, which further comprises a dissolution inhibitor.

[9] The radiation sensitive polysilazane composition according to item[8] above, wherein the dissolution inhibitor is ones selected from thegroup consisting of t-butoxycarbonylated catechol, t-butoxycarbonylatedhydroquinone, t-butyl ester of benzophenone-4,4′-dicarboxylic acid, andt-butyl ester of 4,4′-oxydibenzoic acid, and is contained in an amountof 0.1 to 40% by weight relative to the radiation sensitive polysilazanecomposition.

[10] The radiation sensitive polysilazane composition according to anyone of items [6] to [9] above, wherein the water-soluble compound is acompound with a nitro group.

[11] The radiation sensitive polysilazane composition according to anyone of items [6] to [10] above, wherein the water-soluble compound is acompound having a carbonate.

[12] The radiation sensitive polysilazane composition according to anyone of items [6] to [10] above, wherein the water-soluble compound is apolymer.

[13] The radiation sensitive polysilazane composition according to anyone of items [6] to [12] above, which further comprises a sensitizingdye or pigment (hereinafter, refer as to sensitizing dye).

[14] The radiation sensitive polysilazane composition according to item[13] above, wherein the sensitizing dye is ones selected from the groupconsisting of coumarin, ketocoumarin, derivatives thereof andthiopyrylium salts.

[15] The radiation sensitive polysilazane composition according to anyone of items [6] to [14] above, which further comprises an oxidizationcatalyst.

[16] The radiation sensitive polysilazane composition according to item[15] above, wherein the oxidization catalyst is palladium propionate.

[17] The radiation sensitive polysilazane composition according to anyone of items [6] to [16] above, wherein the radiation sensitivepolysilazane composition is used as an inter-layer dielectric.

[18] A method of forming a patterned inter-layer dielectric, whichcomprises forming a coating film of a radiation sensitive polysilazanecomposition comprising a modified poly(sil sesquiazane) having a numberaverage molecular weight of 100 to 100,000 containing a basicconstituent unit represented by the general formula: —[SiR⁶(NR⁷)_(1.5)]—and other constituent units represented by the general formula: —[SiR⁶₂NR⁷]— and/or —[SiR⁶ ₃ (NR⁷)_(0.5)]— (in the aforementioned formulae, R⁶independently represents a C₁₋₃ alkyl group or a substituted orunsubstituted phenyl group and R⁷ independently represents a hydrogenatom, a C₁₋₃ alkyl group or a substituted or unsubstituted phenyl group)in a ratio of 0.1 to 100 mol-% to said basic constituent unit, a photoacid generator, and a water-soluble compound as a shape stabilizer,patternwise irradiating the coating film, dissolving and removing theirradiated part of the coating film, and leaving the residual patternedcoating film in the ambient atmosphere or burning the coating film.

The patterned polysilazane film formed by the method of this inventioncan be used directly as e.g. an etching resist or a patterned coating ofa constituent unit in devices such as display device. Because theradiation sensitive polysilazane composition to be used in the method ofthis invention is a positive working composition, it has higherresolution. Further it has also higher resistance to oxygen plasma thanthat of conventional resists based on organic materials. In addition,the silica type ceramic film formed by the burning method of thisinvention is a film excellent in heat resistance and having lowdielectric constant and high transparency, etc., and thus it can be usedparticularly preferably as an inter-layer dielectric.

According to this invention, by adding a water-soluble compound as ashape stabilizer to a radiation sensitive polysilazane compositioncomprising a specific modified poly(sil sesquiazane) and a photo acidgenerator as described in item [6] above, the resolution of patterningby light is significantly improved.

Further, by leaving for a long time or burned a coating film formed fromthe radiation sensitive polysilazane composition described in items [6]to [17] above, a patterned silica type ceramic film suitable as aninter-layer dielectric and having excellent properties such as high heatresistance, low dielectric constant, and high transparency can beobtained.

In addition, a sensitizing dye may be contained in the radiationsensitive polysilazane composition thereby enabling patterning using aninexpensive light source such as a high-pressure mercury lamp.

Moreover, an oxidization catalyst may be contained in the radiationsensitive polysilazane composition containing the sensitizing dye,whereby the sensitizing dye can be decomposed at the time of burning thepatterned coating film, and a colorless and transparent silica typeceramic film useful as an inter-layer dielectric in a liquid crystaldisplay or the like can be obtained.

Furthermore, by adding a pigment to the radiation sensitive polysilazanecomposition in the present invention, a color filter and black matrixsuperior in heat resistance, insulating properties and hardness andexcellent in accuracy of pattern can be prepared.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view showing the shape of a side wall ofa pattern section of the radiation sensitive polysilazane compositionwhich does not contain a water-soluble compound as shape stabilizer.

FIG. 2 is a schematic sectional view showing the shape of a side wall ofa pattern section of a radiation sensitive polysilazane compositioncontaining a water-soluble compound as shape stabilizer according to thepresent invention.

FIG. 3 is an IR absorption spectrum of the modified poly(silsesquiazane) used in the radiation sensitive composition of the presentinvention.

FIG. 4 is an IR absorption spectrum of a burned film formed in Examplesin the present-invention.

FIG. 5 is an IR absorption spectrum of a burned film formed inComparative Examples.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, this invention is described in detail.

A method of forming a patterned polysilazane film according to thepresent invention comprises, but is not limited to;

-   (a) a coating film-forming step of forming a coating film on a    substrate by applying or printing the radiation sensitive    polysilazane composition onto the substrate,-   (b) an exposure step of irradiating the coating film with patterned    light,-   (c) a moistening treatment step of bringing the patternwise-exposed    substrate heated if necessary into contact with a gas containing    water vapor, to decompose the polysilazane, and-   (d) a development step of dissolving and removing the    light-irradiated portion of the coating film.

Hereinafter, the method of forming a patterned polysilazane filmaccording to this invention is described in detail by reference to thisexemplified method.

First, in the method of forming a patterned polysilazane film accordingto this invention, there are used, as a radiation sensitive composition,a radiation sensitive composition functioning as a positive type such asa radiation sensitive polysilazane composition comprising a polysilazaneand a photo acid generator.

Typical examples of the polysilazane used in this positive workingradiation sensitive polysilazane composition are as follows;

-   (A) A polysilazane having a number average molecular weight of 100    to 50,000 having a skeleton represented by the general formula:    wherein R¹, R² and R³ independently represent a hydrogen atom,    analkyl group, an alkenyl group, a cycloalkyl group, an aryl group,    other groups wherein an atom bound directly to the silicon or    nitrogen is carbon, an alkylsilyl group, an alkylamino group or an    alkoxyl group,    -   or a modified product thereof.-   (B) A poly(silsesquiazane) having a number average molecular weight    of 100 to 100,000 having a skeleton represented by the general    formula:    —[SiR⁴(NR⁵)_(1.5)]_(n)—  (II)    wherein R⁴ and R⁵ independently represent a hydrogen atom, an alkyl    group, an alkenyl group, a cycloalkyl group, an aryl group which may    have a substituent group, other groups wherein a atom bound directly    to the silicon or nitrogen is carbon, an alkylsilyl group, an    alkylamino group or an alkoxyl group, and n is an arbitrary integer,    -   or a modified product thereof.-   (C) A polyorganosiloxazane having a number average molecular weight    of 300 to 100,000 containing —(RSiN₃)—, —(RSiN₂O)—, —(RSiNO₂)— and    —(RSiO₃)— as main repeating units, wherein R is an alkyl group, an    alkenyl group, a cycloalkyl group, an aryl group, an alkylamino    group or an alkylsilyl group.

Preferable examples of the modified product of the poly(sil sesquiazane)described in (B) above include a modified poly(sil sesquiazane)represented by the following (D).

-   (D) A modified poly(sil sesquiazane) having a number average    molecular weight of 100 to 100,000 containing a basic constituent    unit represented by the general formula:    —[SiR⁶(NR⁷)_(1.5)]—  (III)    and other constituent units represented by the general formula:    —[SiR⁶ ₂NR⁷]—  (IV)    and/or    —[SiR⁶ ₃(NR⁷)_(0.5)]—  (V)    (in aforementioned formulae, R⁶ independently represent a C₁₋₃ alkyl    group or a substituted or unsubstituted phenyl group, R⁷    independently represent a hydrogen atom, a C₁₋₃ alkyl group or a    substituted or unsubstituted phenyl group), wherein the content of    the other constitution unit being 0.1 to 100 mol-%, preferably 0.5    to 40 mol-% and more preferably 1 to 20 mol-% to the basic    constituent unit.

In this modified poly(sil sesquiazane), the other constituent units arebound at random to the basic constituent units. In the modified poly(silsesquiazane), specific groups of R⁶ and R⁷ can be selectedindependently, and therefore these groups may be the same or differentbetween the basic constituent units or between the basic constituentunit and the other constituent unit in a polymer. For example, in thebasic constituent units, a part of R⁶ groups may be methyl while theremainder may be phenyl, and a part of R⁷ groups may be hydrogen whilethe remainder may be methyl; R⁶ group in the basic constituent unit maybe methyl while R⁶ group in the other constituent unit may be methyl orphenyl and R⁷ group in the basic constituent units may be hydrogen whileR⁷ group in the other constituent units may be hydrogen or methyl; andso on. Preferably, R⁶ groups in both the basic constituent unit andother constituent unit are methyl or phenyl group, most preferablymethyl group. Preferably, R⁷ groups in both the basic constituent unitand other constituent unit are hydrogen.

In the modified poly(sil sesquiazane) described in (D) above, when theconstituent unit of the general formula (IV) only is contained as theother constituent units, the ratio of the constituent unit of thegeneral formula (IV) to the above basic constituent unit is preferably0.1 to 100 mol-%, more preferably 1 to 20 mol-%. When the constituentunit of the general formula (V) only is contained as the otherconstituent unit, the ratio of the constituent units of the generalformula (V) to the above basic constituent unit is preferably 0.1 to 50mol-%, more preferably 0.5 to 20 mol-%. When the ratio of the otherconstituent unit is less than 0.1 mol-%, the stability of the resultantpolymer itself is lowered, and the polymer molecules may be mutuallypolymerized during storage. On the other hand, when the ratio of theother constituent unit is greater than 100 mol-%, the molecular weightof the resultant polymer is not sufficiently increased, and thus itscoating is undesirably fluidized.

The number average molecular weight of the modified poly(silsesquiazane) described in (D) above is in the range of 100 to 100,000,preferably 500 to 5000. If the number average molecular weight of themodified poly(sil sesquiazane) is lower than 100, the coating film isfluidized, while if the number average molecular weight is greater than100,000, the poly(sil sesquiazane) is hardly dissolved in a solvent, soeither case is not preferable.

In this invention, as is mentioned above, the word “polysilazane” isused as the one containing poly(sil sesquiazane), polyorganosiloxazaneand the like.

In this invention, the polysilazane may naturally be one kind ofpolysilazane or two or more kinds of polysilazane, or may be a copolymerof a polysilazane with another polymer or a mixture of a polysilazaneand another polymer or compound. The polysilazane used includes the onehaving a linear, cyclic or cross-linked structure, or the one having aplurality of these structures in the molecule, and these polysilazanescan be used alone or as a mixture thereof. As these polysilazanes,perhydropolysilazanes are preferable in respect of the hardness anddenseness of the resultant film, and organopolysilazanes are preferablein respect of flexibility. Depending on the intended use, selection ofthese polysilazanes can be conducted suitably by those skilled in theart.

The polysilazanes described above are known or can be produced by aknown method. Specifically, production of polysilazanes is described ine.g. JP-B 63-16325, JP-A 61-89230, JP-A 62-156135, D. Seyferthetal.:Communication of Am. Cer. Soc., C-13, January (1983), Polym. Prepr., Am.Chem. Soc., Div. Polym. Chem., 25, 10 (1984), etc.

Further, the polysilazanes having a cross-linked structure in themolecule may be those reported in JP-A 49-69717, D. Seyferth et al.:Communication of Am. Cer. Soc., C-132, July (1984) orpolymetalosilazanes containing a metal atom in the structure.

Besides, the following polysilazanes can be similarly used: thepolysiloxazanes whose repeating units are represented by[(SiH₂)_(n)(NH)_(m)] and [(SiH₂)_(r)O] (wherein n, m and r eachrepresent 1, 2 or 3) as reported in JP-A 62-195024; thepolyborosilazanes excellent in heat resistance produced by reacting aboron compound with a polysilazane as reported in JP-A 2-84437; thepolymetalosilazanes produced by reacting a polysilazane with a metalalkoxide as reported in JP-A 63-81122, JP-A 63-191832 and JP-A 2-77427;the inorganic silazane polymers having high molecular weight or modifiedpolysilazanes having an increased molecular weight as reported in JP-A1-138108, JP-A 1-138107, JP-A 1-203429 and JP-A 1-203430, or havingimprovements in hydrolysis resistance as reported in JP-A 4-63833 andJP-A 3-320167; the copolymerized polysilazanes advantageous for formingthick film and having organic components introduced into polysilazanesas reported in JP-A 2-175726, JP-A 5-86200, JP-A 5-331293 and JP-A3-31326; and the polysilazanes to be converted into ceramics at lowertemperatures and capable of application onto plastics or metals such asaluminum, to which a catalytic compound has been added for promotingconversion of polysilazanes into ceramics, as reported in JP-A 5-238827,JP-A 6-122852, JP-A 6-299188, JP-A 6-306329, JP-A 6-240208 and JP-A7-196986.

The polysilazane which can be used preferably in this invention ispoly(sil sesquiazane) having a number average molecular weight of 100 to100,000, preferably 300 to 10,000 and having mainly a skeletonrepresented by the general formula (II) above, or a derivative thereof.Further, more preferred poly(sil sesquiazane) is polymethylsilazanewherein R⁴ is a methyl group and R⁵ is a hydrogen atom in the formula(II), or polyphenylsilazane wherein R⁴ is a phenyl group and R⁵ is ahydrogen atom in the formula (II). Such polysilazanes can be easilyobtained by using R⁴SiCl₃ as a starting material in ammonolysis insynthesis of usual polysilazanes. For the ammonolysis in synthesis ofpolysilazanes, reference is made to e.g. JP-B 63-16325.

The polyorganosiloxazane mentioned in (C) above is also a polysilazaneused preferably in the invention. This polyorganosiloxazane can beproduced by reacting an organic halosilane represented by the generalformula R_(n)SiX_(4−n) (wherein R is an alkyl group, an alkenyl group, acycloalkyl group, an aryl group, an alkylamino group or an alkylsilylgroup, X is a halogen atom, and n is 1 or 2) with ammonia and water.Such polyorganosiloxazane can give a burned film with a low dielectricconstant even when treated at high temperatures, so it is usefulparticularly as a precursor of inter-layer dielectric. Another advantageof the polyorganosiloxazane is that by changing the content of oxygen inthe main chain, the relative dielectric constant of the resultant burnedfilm can be regulated to achieve a desired relative dielectric constanteasily. For a detailed description of such polyorganosiloxazane and amethod of producing the same, reference is made to Japanese PatentApplication No. Hei 10-528633 (WO98/029475).

In this invention, the modified poly(sil sesquiazane) described in (D)above can be used particularly preferably as the polysilazane. Thismodified poly(sil sesquiazane) can be easily obtained by using thestarting materials R⁶SiCl₃, R⁶ ₂SiCl₂ and/or R⁶ ₃SiCl in ammonolysis insynthesis of conventional polysilazanes, wherein the latter twomaterials are used in a molar ratio corresponding to the content of theother constituent units. For example, when the unit of the generalformula —[SiR⁶ ₂NR⁷]— is contained in an amount of 20 mol-% as the otherconstituent unit, starting silane materials containing 20 mol-% R⁶₂SiCl₂ mixed with R⁶SiCl₃ may be subjected to ammonolysis, and when theunits of the general formula —[SiR⁶ ₃(NR⁷)_(0.5)]— are contained in anamount of 10 mol-% as the other constituent units, 10 mol-% R⁶ ₃SiCl maybe mixed with R⁶SiCl₃. For a detailed description of ammonolysis insynthesis of polysilazanes, reference is made to e.g. JP-B 63-16325.

The modified poly(sil sesquiazane) described in (D) above is highlystable and substantially free from further polymerization duringstorage, so its molecular weight is prevented from being increased.Though not bound by a specific theory, the reason for preventing anincrease in the molecular weight of this polymer is estimated asfollows. The polymer consisting exclusively of trifunctional basicconstituent units has a large number of distorted cyclic structures inthe molecule, thus permitting the structures to be cleaved duringstorage and the cleaved sites to be bound again to other similarlycleaved molecules to increase the molecular weight; however, when thebifunctional and/or monofunctional constituent units are introduced intothe trifunctional basic units, the distorted cyclic structures aredecreased thereby making occurrence of such cleavage and re-bindingdifficult, to prevent an increase in the molecular weight of thepolymer.

The radiation sensitive composition of this invention or used in thisinvention includes a photo acid generator. The photo acid generator isexcited directly by irradiation with light in its inherent radiationsensitive wavelength range, or when a sensitizing dye is used, the photoacid generator is excited indirectly by light in a wavelength rangewhere the sensitizing dye is excited. It is estimated that by the photoacid generator in an excited state, Si—N linkages in the polysilazaneare cleaved, and the cleaved Si—N linkages react with water to formsilanol (Si—OH) linkages. Because the silanol is soluble in a developingsolution described later, and thus only the irradiated portion of thecoating film of the radiation sensitive composition is dissolved andremoved to achieve positive type patterning.

Specifically, the photo acid generator used in this positive workingradiation sensitive polysilazane composition includes e.g. peroxides,naphthoquinone diazide sulfonate, nitrobenzyl ester, etc. Further,benzoin tosylate is also useful. Other useful photo acid generatorsinclude nitrobenzyl sulfonic acids, onium salts [for example,bis(4-t-butylphenyl)iodonium salt and triphenyl sulfonium salt], etc. Ifnecessary, two or more of these photo acid generators can be used incombination.

Hereinafter, the photo acid generators of peroxide type, naphthoquinonediazide sulfonate type and nitrobenzyl ester type are enumerated.However, the following examples are listed for merely illustrativepurposes, and the photo acid generator used in this invention is notlimited to those enumerated below.

Peroxide Type Photo Acid Generator

3,3′,4,4′-tetra(t-butylperoxycarbonyl)benzophenone, t-butylperoxybenzoate, methyl ethyl ketone peroxide, cyclohexanone peroxide,methylcyclohexanone peroxide, methyl acetoacetate peroxide, acetylacetone peroxide, 1,1-bis(t-hexylperoxy)3,3,5-trimethyl cyclohexane,1,1-bis(t-hexylperoxy)cyclohexane, 1,1-bis(t-butylperoxy)3,3,5-trimethylcyclohexane, di-t-butylperoxy-2-methyl cyclohexane,1,1-bis(t-butylperoxy)cyclohexane, 1,1-bis(t-butylperoxy)-cyclododecane,2,2-bis(t-butylperoxy)butane, n-butyl 4,4-bis(t-butylperoxy)valerate,2,2-bis(4,4-di-t-butylperoxycyclohexyl)propane, p-menthanehydroperoxide,diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethyl butyl hydropentylperoxide, cumene hydroperoxide, t-hexyl hydroperoxide,t-butylhydroperoxide, α,α′-bis(t-butylperoxy)diisopropylbenzene, dicumylperoxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, t-butylcumylperoxide, di-t-butyl peroxide,2,5-dimethyl-2,5-bis(t-butylperoxy)hexyne-3, isobutyryl peroxide,3,5,5-trimethyl hexanoyl peroxide, octanoyl peroxide, lauroyl peroxide,stearoyl peroxide, succinic acid peroxide, m-toloyl benzoyl peroxide,benzoyl peroxide, di-n-propyl peroxydicarbonate, diisopropylperoxydicarbonate, bis(4-t-butylcyclohexyl)peroxydicarbonate,di-2-ethoxyethyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate,di-3-methoxybutyl peroxydicarbonate,di(3-methyl-3-methoxybutyl)peroxydicarbonate,α,α′-bis(neodecanoylperoxy)diisopropyl benzene, cumylperoxyneodecanoate, 1,1,3,3-tetramethylbutyl peroxyneodecanoate,1-cyclohexyl-1-methylethyl peroxyneodecanoate, t-hexylperoxyneodecanoate, t-butyl peroxyneodecanoate, t-hexyl peroxypivalate,t-butyl peroxypivalate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, 2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane,1-cyclohexyl-1-methylethylperoxy-2-ethyl hexanoate, t-hextylperoxy2-ethyl hexanoate, t-butylperoxy 2-ethyl hexanoate, t-butylperoxyisobutyrate, t-hexylperoxy isopropyl monocarbonate, t-butylperoxy maleicacid, t-butylperoxy 3,5,5-trimethyl hexanoate, t-butyl peroxylaurate,2,5-dimethyl-2,5-(m-toloylperoxy)hexane, t-butyl peroxyisopropylmonocarbonate, t-butyl peroxy 2-ethylhexyl monocarbonate, t-hexylperoxybenzoate, 2,5-dimethyl-2,5-bis(benzoylperoxy)hexane, t-butylperoxyacetate, t-butylperoxy-m-toloyl benzoate,bis(t-butylperoxy)isophthalate, t-butyl peroxy allyl monocarbonate,t-butyltrimethylsilyl peroxide, 1,3-di(t-butylperoxydicarbonyl)benzene,etc.

Naphthoguinonediazide Sulfonate Type Photo Acid Generator

1,2-naphthoquinone-(2)-diazide-5-sulfonic acid chloride,1,2-naphthoquinone-(2)-diazide-4-sulfonic acid chloride, (mono totri)esters between 2,3,4-trihydroxybenzophenone and6-diazo-5,6-dihydro-5-oxo-naphthalene-1-sulfonic acid, (mono totri)esters between 2,3,4,4′-trihydroxybenzophenone and6-diazo-5,6-dihydro-5-oxo-naphthalene-1-sulfonic acid, etc.

Nitrobenzyl Ester Type Photo Acid Generator

Nitrobenzyl tosylate, dinitrobenzyl tosylate, nitrobenzyl chloride,dinitrobenzyl chloride, nitrobenzyl bromide, dinitrobenzyl bromide,nitrobenzyl acetate, dinitrobenzyl acetate, nitrobenzyltrichloroacetate, nitrobenzyl trifluoroacetate, etc.

The content of these photo acid generators in the radiation sensitivepolysilazane composition shall be a suitable amount depending on thetype of the photo acid generator and the use of the radiation sensitivecomposition, and the amount of the photo acid generator is generally0.05 to 50% by weight, preferably 0.1 to 20% by weight, more preferably1 to 20% by weight relative to the weight of the polysilazane. If thecontent of the photo acid generator is less than 0.05% by weight, therate of decomposition reaction is significantly decreased, while if thecontent is greater than 50% by weight, e.g. the resultant modifiedpoly(sil sesquiazane) may hardly give a characteristic dense filmderived from modified poly(sil sesquiazane).

When the radiation sensitive composition comprising the polysilazane,for example the modified poly(sil sesquiazane) and the photo acidgenerator should be stored over a predetermined time, some photo acidgenerators, for example nitrobenzyl sulfonate, may be decomposed by avery small amount of NH₃ released from the polysilazane in the radiationsensitive composition during storage. In this case, the storagestability of the radiation sensitive composition can be improved byselecting an alkali-resistant photo acid generator. The alkali-resistantphoto acid generator includes not only iminosulfonate derivatives,disulfone derivatives and diazomethane derivatives, but also sulfoximetype compounds such as4-methoxy-α-((((4-methoxyphenyl)sulfonyl)oxy)imino)benzene acetonitrileand triazine type compounds, for example the following compounds.

By adding a water-soluble compound as a shape stabilizer to theradiation sensitive polysilazane composition, the resolution can furtherbe improved. This effect is particularly significant when thepolysilazane used is the modified poly(sil sesquiazane) shown in (D)above. The shape stabilizer refers to an agent by which the side wall ofa pattern section formed by removing an irradiated portion can be madefurther steep.

As described above, Si—N linkages in the polysilazane are cleaved byirradiation and then react with water in the atmosphere to form silanollinkages. By this reaction, formation of silanol linkages rapidly occursin the coating film near to the surface in contact with a hydrousatmosphere. However, the polysilazane e.g. the modified poly(silsesquiazane) shown in (D) above is highly hydrophobic so that the amountof water permeating into the coating film via the surface thereof isdecreased at a site nearer to the interface of the substrate coated, andthus formation of silanol linkages hardly occurs in an internal part ofthe coating film not contacting with the hydrous atmosphere.Accordingly, the sensitivity of the modified poly(sil sesquiazane)coating film is decreased from the surface of the coating film to theinterface of the substrate, to bring about a difference in sensitivitytherebetween. The present inventors found that this difference insensitivity causes the following problem.

As shown in FIG. 1, a modified poly(sil sesquiazane) coating film 5 hasnot only a part irradiated directly with light via an opening of a mask1 but also a part 4 irradiated indirectly due to irradiation “oozing”into the modified poly(sil sesquiazane) shielded by the mask 1. Now,when the difference in sensitivity described above occurs in the coatingfilm, silanol linkages are formed more easily in a site nearer to thesurface of the coating film and thus easily dissolved and removed bysubsequent development. As a result, a side wall 3 of the patternsection slopes gently as shown in FIG. 1, and this phenomenon was foundto be one factor limiting fine patterning or improvement in resolution.

The present inventors found that when a water-soluble compound is addedas a shape stabilizer, the side wall of a pattern section can be madesteep to improve resolution. That is, by adding the water-solublecompound, the hydrophobicity of the radiation sensitive coating film isdecreased, thus promoting the access of water from the surface of thecoating film in contact with the hydrous atmosphere to the inside of thecoating film. Accordingly, the difference in the rate of formation ofsilanol linkages between the vicinity of the surface of the coating andthe vicinity of the interface of the substrate , that is, the differencein sensitivity is decreased. Thus, the irradiation energy necessary forsufficiently dissolving and removing the region ranging from the part ofthe coating film corresponding to the opening of the mask to thevicinity of the interface of the substrate can be reduced, and inconsequence, the energy of “oozing light” into the part shielded by themask can be reduced. In the part where the energy of “oozing light” isreduced to be too low to cleave Si—N linkages in the modified poly(silsesquiazane), as silanol linkages are not formed, the part 4 irradiatedindirectly with “oozing light” is not dissolved or removed at the timeof development. As a result, the range of the coating film dissolved andremoved in the part shielded by the mask is reduce, whereby the sidewall 3 of the pattern section is made steep, and most preferably theside wall stands upright as shown in FIG. 2.

It can be easily understood that the side wall of the pattern sectioncan be made steep regardless of the sensitivity of the radiationsensitive composition. That is, when the sensitivity of the radiationsensitive composition in the vicinity of the substrate is increased, theside wall of the pattern section is made steep by decreasing the energyof irradiation as described above. When the sensitivity of the radiationsensitive composition is reduced as a whole by adding e.g. the watersoluble compound according to this invention, the energy of irradiationnecessary for sufficiently dissolving and removing the region rangingfrom the part of the coating corresponding to the opening of the mask tothe vicinity of the interface of the substrate should be increased insome cases, but the energy of “oozing light” necessary for cleaving Si—Nlinkages in the mask-shielded portion of the modified poly(silsesquiazane) is also increased. Therefore the side wall of the patternsection is made similarly steep in the case that the difference insensitivity of the coating is low. In short, regardless of thesensitivity of the radiation sensitive composition, the side wall of thepattern section is made steep by reducing the difference in sensitivitybetween the vicinity of the surface of the coating and the vicinity ofthe interface of the substrate.

The water-soluble compound even if insoluble in neutral water is usefulinsofar as it is soluble in acidic water or alkaline water. This isbecause when the water-soluble compound is soluble in acidic water, thelight-exposed part is made acidic by an acid generated from the photoacid generator, and when it is soluble in alkaline water, thepermeability of an developing solution is promoted at the time ofdevelopment with an aqueous alkaline solution. In either case, theaccess of water from the surface of the coating to the inside of thecoating is promoted, and thus the difference in sensitivity between thevicinity of the surface of the coating and the vicinity of the interfaceof the substrate is reduced.

The water-soluble compound in this invention may be a single compound orpolymer. The solubility of the water-soluble compound may be about atleast 0.01 g/100 milliliters in neutral water, acidic water or alkalinewater, and it is not always necessary for the water-soluble compound tobe readily soluble. As described later, it is preferable that thewater-soluble compound is uniformly mixed with the radiation sensitivecomposition, and thus it should have sufficient compatibility with thepolysilazane and the solvent.

Examples of such compounds include 2-nitroaniline, 3-nitroaniline,4-nitroaniline, 2-nitro-4-aminotoluene, 3-nitro-2-aminotoluene,3-nitro-4-aminotoluene, 4-nitro-2-aminotoluene, 5-nitro-2-aminotoluene,6-nitro-2-aminotoluene, 4-nitrobenzene-azo-orcinol, 1-(4-nitrobenzenesulfonyl)-1H-1,2,4-triazole, 5-nitrobenzimidazole, 4-nitrobenzylacetate, 2-nitrobenzyl alcohol, 3-nitrobenzyl alcohol, 4-nitrobenzylalcohol, nitrocyclohexane, 1-nitropropane, 2-nitropropane, nifedipin,2,7-dinitrofluone, 2,7-dinitro-9-fluorenone, 3,3′-dinitrobenzophenone,3,4′-dinitrobenzophenone, propylene carbonate, ethylene carbonate, amidecompounds such as trifluoroacetoamide, trifluoroacetate ammonium salt,water-soluble acrylic polymer, water-soluble epoxy polymer,water-soluble melamine polymer, etc. Particularly preferablewater-soluble compounds are 2-nitroaniline, 3-nitroaniline,4-nitroaniline, 2-nitro-4-aminotoluene, propylene carbonate, ethylenecarbonate and water-soluble acrylic polymer.

The water-soluble compound is added as a shape stabilizer in an amountof usually 0.01 to 50% by weight of the polysilazane, for example themodified poly(sil sesquiazane). The optimum mixing ratio is varieddepending on the characteristics of the individual water-solublecompounds, but if the content is less than 0.01% by weight, the effectof improving the slope of the pattern wall is not sufficient, while ifthe content is greater than 50% by weight, there occurs problems such asdefects and insufficient strength in the physical properties of the filmafter development. The amount of the water-soluble compound added ispreferably 0.05 to 40% by weight, more preferably 0.1 to 30% by weightrelative to the polysilazane.

The radiation sensitive composition is prepared by adding the photo acidgenerator and the water-soluble compound as the shape stabilizer to thepolysilazane. The photo acid generator and the water-soluble compoundare preferably uniformly mixed, and for this mixing, it is preferablethat the polysilazane, the photo acid generator and the water-solublecompound are mixed under vigorous stirring, or the respective componentsare mixed after dissolved in a solvent described later. In particular,when the photo acid generator and the water-soluble compound are solid,it is preferable that the components are once dissolved in the solventand then mixed.

When these components are added, the temperature and pressure are notparticularly limited, and they can be added at room temperature andatmospheric pressure. However, the procedures from the addition step tothe development step described later are conducted desirably inenvironments not containing light having the radiation sensitivewavelength of the photo acid generator used, preferably in a dark place,in order to prevent excitation of the photo acid generator.

The radiation sensitive polysilazane composition comprising thepolysilazane and the photo acid generator used in this invention maycontain a sensitizing dye if necessary. For example, there is a photoacid generator such as 3,3′,4,4′-tetra(t-butylperoxycarbonyl)benzophenone, which is excited at awavelength shorter than about 330 nm. When the photo acid generatorwhose radiation sensitive range is in such a short-wavelength range isirradiated with light by an excimer laser such as KrF type (248 nm), ArFtype (193 nm), etc., the photo acid generator is directly excited by theirradiation, thus making it unnecessary to use a sensitizing dye.However, when an inexpensive light source such as a high-pressuremercury lamp (360 to 430 nm) is used, the photo acid generator can beexcited indirectly by combining it with a sensitizing dye to be excitedin the corresponding wavelength range, and the exposure can be conductedusing an inexpensive light source such as a high-pressure mercury lamp(360 to 430 nm). The sensitizing dye includes coumarin, ketocoumarin andderivatives thereof, pyrylium salts, thiopyrylium salts, and dyes suchas cyanine dyes, carbocyanine dyes and styryl dyes. These sensitizingdyes are used in an amount of usually 0.05 to 50% by weight, preferably1 to 20% by weight relative to the polysilazane.

Specifically, the sensitizing dye used in the radiation sensitivepolysilazane composition includes p-bis(o-methylstyryl)benzene,7-dimethylamino-4-methylquinolon-2, 7-amino-4-methylcoumarin,4,6-dimethyl-7-ethylaminocoumarin, 2-(p-dimethylaminostyryl)-pyridylmethyl iodide, 7-diethylaminocoumarin, 7-diethylamino-4-methylcoumarin,2,3,5,6-1H,4H-tetrahydro-8-methylquinolidino-<9,9a,1-gh>coumarin,7-diethylamino-4-trifluoromethylcoumarin,7-dimethylamino-4-trifluoromethylcoumarin,7-amino-4-trifluoromethylcoumarin,2,3,5,6-1H,4H-tetrahydroquinolidino-<9,9a,1-gh>coumarin,7-ethylamino-6-methyl-4-trifluoromethylcoumarin,7-ethylamino-4-trifluoromethylcoumarin,2,3,5,6-1H,4H-tetrahydro-9-carboethoxy-quinolidino-<9,9a, 1-gh>coumarin,3-(2′-N-methylbenzimidazolyl)-7-N,N-diethylaminocoumarin,N-methyl-4-trifluoromethyl-pyperidino-<3,2-g>coumarin,2-(p-dimethylaminostyryl)-benzo-thiazolyl ethyl iodide,3-(2′-benzimidazolyl)-7-N,N-diethylamino coumarin, and3-(2′-benzothiazolyl)-7-N,N-diethylaminocoumarin, as well as pyryliumsalts and thiopyrylium salts represented by the following formula:

X R₁ R₂ R₃ Y S OC₄H₉ H H BF₄ S OC₄H₉ H H BF₄ S OC₄H₉ OCH₃ OCH₃ BF₄ S HOCH₃ OCH₃ BF₄ S N(CH₃)₂ H H ClO₂ O OC₄H₉ H H SbF₆

Other examples of the sensitizing dye include the following compounds:

Particularly preferable sensitizing dyes are 7-diethylamino-4-methylcoumarin and 7-diethylamino-4-trifluoromethyl coumarin.

When the sensitizing dye is used, the resultant coating may be colored.When the coating is used as a resist such as an etching resist, theresist is removed after desired patterning processing is finished, andthus coloration of the resist is hardly problematic. However, when thepatterned coating is burned and used without removing the coating afterpatterning, for example when the burned coating is used as aninter-layer dielectric in a display, there are some cases where theburned coating should be transparent to visible rays. In these casestoo, the coloration is hardly problematic because when the coating isburned, the sensitizing dye is generally decomposed by the photo acidgenerator contained in the radiation sensitive polysilazane composition,to make the coating transparent. However depending on the intended use,there are some cases where the coating should be further transparent andcolorless. In these cases, an oxidization catalyst capable ofdecomposing the sensitizing dye during burning of the coating but notparticipating in the photo-reaction may be added separately to theradiation sensitive polysilazane composition. Examples of suchoxidization catalysts include organic metallic compounds and fineparticles such as palladium propionate, palladium acetate, acetylacetonate platinum, ethyl acetonate platinum, fine palladium particles,and fine platinum particles. When the oxidization catalyst is added, theamount of the oxidization catalyst is generally 0.05 to 10% by weight,preferably 0.1 to 5% by weight relative to the polysilazane. By addingthe oxidization catalyst, the unnecessary dye can be decomposed anddiscolored, and simultaneously conversion of the polysilazane intoceramics can be promoted.

By adding a pigment to the radiation sensitive polysilazane composition,a color filter or black matrix superior in heat resistance, insulatingproperties and hardness and excellent in accuracy of pattern can beobtained. Examples of pigments that can be added to the polysilazanecomposition include graphite, carbon black, titanium black, ironoxide,copperchromium black, copperiron manganese black, cobalt iron chromiumblack, etc. The amount of the pigment added is generally 0.05 to 1000%by weight, preferably 10 to 500% by weight relative to the polysilazane.

To improve the efficiency of development, a compound known as theso-called dissolution inhibitor in this technical field can be added tothe radiation sensitive polysilazane composition. The generaldissolution inhibitor can, owing to its hydrophobicity, prevent thepolymer in the unexposed portion of the coating film from beingdissolved in an alkali developing solution, while in the light-exposedportion, the dissolution inhibitor itself is rendered hydrophilic bydegradation by exposure to light or by the photo acid generator, thuspromoting the decomposition of the polymer. As described above, thepolysilazane is not dissolved in the developing solution, and thus theadvantage of the ability of the dissolution inhibitor to preventdissolution of the unexposed portion is hardly enjoyed, but the abilitythereof to promote dissolution of the exposed portion was found to actadvantageously. That is, the rate of dissolution of the light-exposedportion is increased by adding the so-called dissolution inhibitor tothe radiation sensitive polysilazane composition, and in consequence,the efficiency of development can be improved. Examples of suchdissolution inhibitors include t-butoxycarbonyl (hereinafter refer to as“t-BOC”) catechol, t-BOC hydroquinone, t-butyl ester ofbenzophenone-4,4′-dicarboxylic acid, t-butyl ester of 4,4′-oxydibenzicacid, etc. The dissolution inhibitor can be added in the range of 0.1 to40% by weight, preferably 1 to 30% by weight relative to the radiationsensitive composition.

When a solvent is used in the radiation sensitive polysilazanecomposition, it is preferable to use as a solvent, for example, aromaticcompounds such as benzene, toluene, xylene, ethylbenzene,diethylbenzene, trimethylbenzene and triethylbenzene; cyclohexane;cyclohexene; decahydronaphthalene; dipentene; saturated hydrocarboncompounds such as n-pentane, i-pentane, n-hexane, i-hexane, n-heptane,i-heptane, n-octane, i-octane, n-nonane, i-nonane, n-decane andi-decane; ethylcyclohexane; methylcyclohexane; p-menthane; ethers suchas dipropyl ether and dibutyl ether; ketones such as methyl isobutylketone (MIBK); esters such as butyl acetate, cyclohexyl acetate, butylstearate and ethyl lactate; ethylene glycol monoalkyl ethers such asethylene glycol monomethyl ether and ethylene glycol monoethyl ether;ethylene glycol monoalkyl ether acetates such as ethylene glycolmonomethyl ether acetate and ethylene glycol monoethyl ether acetate;propylene glycol monoalkyl ethers such as propylene glycol monomethylether and propylene glycol monoethyl ether; and propylene glycolmonoalkyl ether acetates such as propylene glycol monomethyl etheracetate (PGMEA) and propylene glycol monoethyl ether acetate. When thesesolvents are used, two or more solvents may be mixed in order toregulate the solubility of the polysilazane or the rate of evaporationof the solvents.

The amount (proportion) of the solvent used is determined inconsideration of easiness in operation in the coating method used, thesolubility of each component in the radiation sensitive composition, thecoating property of the radiation sensitive composition and thethickness of the coating film. The solubility is also varied dependingon the average molecular weight, the distribution of molecular weights,and the structure of the polysilazane used. The solvent is useddesirably in an amount such as the concentration of polysilazane beingmade usually 0.1 to 50% by weight, more preferably 0.1 to 40% by weightin consideration of the stability, production efficiency, coatingproperty and so on of the polysilazane.

The radiation sensitive composition of this invention can containsuitable fillers and/or extenders if necessary. Examples of the fillersinclude fine powders of oxide type inorganic materials such as silica,alumina, zirconia and mica or non-oxide type inorganic materials such assilicon carbide, silicon nitride, etc. Depending on the intended use,metallic powders such as aluminum, zinc, copper, etc. can also be added.As these fillers, there may be used ones having various forms such asneedle (including whiskers), granular and scale forms singly or as amixture of two or more kinds thereof. Further, the particle size ofthese fillers is desirably smaller than the thickness of the coatingfilm which can be applied once. The amount of the fillers added is inthe range of 0.05 to 10 parts by weight, particularly preferably in therange of 0.2 to 3 parts by weight per part by weight of thepolysilazane.

The radiation sensitive composition of this invention may furthercontain a leveling agent, a deforming agent, an antistatic agent, a Lwabsorber, apH adjuster, adispersant, asurfacemodifier, a plasticizer, adrying promoter, and an anti-sagging agent if necessary.

The radiation sensitive polysilazane composition is applied onto anarbitrary substrate such as silicon substrate, glass substrate, etc. bya known coating method such as roll coating, dip coating, bar coating,spin coating, spray coating, flow coating and brushing, to form acoating film thereon. A printing method may be used in place of thecoating method. In this invention, the coating film encompasses a filmformed by a printing method. If necessary, the coating is dried andpre-baked (heat-treated) in order to decrease the amount of gas to beremoved. Pre-baking can be conducted at a temperature of 40 to 200° C.,preferably 60 to 120° C., for 10 to 180 seconds, preferably 30 to 90seconds on a hot plate or for 1 to 30 minutes, preferably 5 to 15minutes in a clean oven. If necessary, the radiation sensitivecomposition may be applied repeatedly until the desired thicknesscoating is obtained. The desired thickness is for example 0.05 to 2 μmfor photoresist, 0.5 to 4 μm for an inter-layer dielectric, or 0.3 to 3μm for color filter or black matrix.

The coating film formed from the radiation sensitive polysilazanecomposition is then exposed with light. In this exposure step, a lightsource such as high-pressure mercury lamp, low-pressure mercury lamp,metal halide lamp, xenon lamp, excimer laser, X-rays, electron rays,etc. can be used depending on the radiation sensitive range of theradiation sensitive polysilazane composition. Patternwise lightirradiation is conducted usually using a photo mask. Except forultra-fine processing such as semiconductor processing, there is used alight having wavelength of 360 to 430 nm (light from high-pressuremercury lamp) generally as the irradiation light. Particularly, a lightof 430 nm in wavelength is often used for a liquid crystal display. Inthese cases, a combination of the radiation sensitive composition ofthis invention and the sensitizing dye can be advantageously used asdescribed above.

The amount of light energy irradiated in exposure is varied depending onthe light source used and the thickness of the coating, but is usually0.05 mJ/cm² or more, desirably 0.1 mJ/cm² or more. There is noparticular upper limit, but it is not practical that a dose ofirradiation is set in too high levels because of possibility of halationand from the relationship with the treatment time. It is usuallypreferable that the amount of light energy irradiated is not greaterthan 1000 mJ/cm². Exposure may be conducted generally in the ambientatmosphere (in the air) or in a nitrogen atmosphere, but an atmosphereenriched in oxygen may also be used in order to promote decomposition ofthe polysilazane.

By exposure of the radiation sensitive polysilazane compositioncontaining the photo acid generator, an acid is generated in thelight-exposed portion, whereby Si—N linkages in the polysilazane arecleaved and react with moisture in the ambient atmosphere. Inconsequence silanol (Si—OH) linkages are formed and the polysilazane isdecomposed. It is particularly desirable that the radiation sensitivepolysilazane exposed is subjected to moistening treatment. When water isfed continuously to the film by this moistening treatment, the acid oncecontributed to cleavage of Si—N linkages acts repeatedly as a cleavingcatalyst to promote conversion into SiOH. Accordingly, as the humidityof the gas to be contacted with the radiation sensitive polysilazanecomposition is increased, the rate of decomposition of the polysilazaneis also increased. But when the humidity of the gas is too high, thereis a danger of condensation of the moisture in the gas on the surface ofthe film formed from the radiation sensitive polysilazane composition.If moisture condensation occurs, there are instances where decompositionof the polysilazane proceeds in only a surface area of the film. Thereason is estimated as condensed water can move only as an apparentlylarge molecule due to hydrogen bonding. Further there are instanceswhere a part of the light-exposed region cannot be removed bydevelopment with an aqueous alkaline solution, that is, developmentresidues may also occur. The reason is estimated as the rate ofdecomposition of the portion to which condensed water adheres isdecreased. Accordingly, the humidity of the gas should be regulated insuch a range that moisture condensation does not occur on the surface ofthe coating film. The humidity of the gas expressed in terms of relativehumidity to the temperature of the substrate is 35% RH or more,preferably 40% RH or more and more preferably 50% RH or more. There isno particular upper limit of the relative humidity, but moisturecondensation may occur at too high humidity as described above, and fromthis viewpoint, a gas with a relative humidity of 90% RH or less can bepractically used.

In this step of moistening the polysilazane, a gas containing watervapor is contacted with the film on the substrate. For bringing thelight-exposed film of the radiation sensitive polysilazane compositioninto contact with the gas containing water vapor, the substrate havingthe light-exposed film of the radiation sensitive polysilazanecomposition is usually placed in a moistening treatment apparatus, and agas containing water vapor may be introduced continuously to thistreatment apparatus. If necessary, the humidity of the gas to beintroduced may be increased by increasing the moisture in the gas to becontacted with the coating film. If the capacity of the treatmentapparatus is large and the apparatus contains water in an amount enoughto decompose the coating film, the gas containing water vapor may not becontinuously supplied to the treatment apparatus, and only water vapormay be supplied to the treatment apparatus instead of the gas containingwater vapor. From the viewpoint of prevention of moisture condensation,it is preferred that the substrate is placed on e.g. a heating plate andheated during the moistening treatment. By heating the substrate, theadhesion between the substrate and the radiation sensitive polysilazanecoating film is also improved. The substrate is kept in theaforementioned state for a predetermined time such as preventing anexcess of water vapor from contacting with the substrate, and then thesubstrate is brought out and returned to room temperature.

As the heating temperature of the substrate is increased, moisturecondensation hardly occurs on the surface of the coating film.Accordingly, it is preferred that the heating temperature of thesubstrate is higher because the absolute amount of water vapor containedin the gas can be set at higher levels. The heating temperature is madeat room temperature or more, desirably 30° C. or more, but attentionshould be paid at a temperature of 100° C. or more because the partialpressure of water vapor cannot be increased without using a pressuringheating humidifier. Further, at too high temperatures, SiOH formed bymoistening may be converted into SiOSi insoluble in an aqueous alkalinesolution. Accordingly, the upper limit of practical temperature is about100° C. The moistening treatment has been described in detail byreference to a mode wherein the substrate is placed in the treatmentapparatus, but can naturally be conducted in the air without using thetreatment apparatus. Heating of the substrate may be conducted in anarbitrary manner, for example by heating it on a heating plate asdescribed above or by previously heating a gas to be used in themoistening treatment and then introducing the gas into the moisteningtreatment apparatus.

After the step of promoting decomposition of the polysilazane, the filmof the radiation sensitive polysilazane composition is developed with analkali developing solution by a known development method such as paddledevelopment, dip development and shower development. By thisdevelopment, the light-exposed portion of the film of the radiationsensitive polysilazane composition is removed while the unexposedportion remains on the substrate to form a positive pattern thereon.Since the unexposed portion of the polysilazane film is not swollen bythe alkali developing solution, the pattern of the irradiation lightcoincides almost completely with the pattern of the polysilazanedecomposed and removed, thus achieving excellent pattern accuracy.

The alkali developing solution includes e.g. an aqueous solution oftetramethyl ammonium hydroxide (TMAH), choline, sodium silicate, sodiumhydroxide, potassium hydroxide or the like. The concentration of thealkali may be determined in consideration of various conditions such asthe material to be developed, the rate of development required,resolution, etc., but the alkali developing solution used as thestandard in the industry, that is, about 2% aqueous TMAH, isconveniently used. When the polysilazane film is used as an etchingpattern for semiconductor devices or as an inter-layer dielectric afterconversion into silica type ceramics, an aqueous alkali solution freefrom metal ions is preferably used as the developing solution. The timenecessary for development is varied depending on the thickness of thefilm and the developing solution used, but is generally 0.1 to 5minutes, preferably 0.5 to 3 minutes. The temperature for developmenttreatment is generally 20 to 50° C., preferably 20 to 30° C.

After development, the patterned polysilazane film is rinsed with purewater as necessary, dried and used directly as an etching mask, orrinsed with pure water and left for a long time e.g. 1 day or more orsubjected to burning thereby being converted into a silica type ceramicfilm usable as e.g. an inter-layer dielectric. The burning temperatureand burning time are varied depending on the constitution of theradiation sensitive polysilazane composition, the thickness of thecoating film and the heat resistance of the substrate, electronic parts,etc. But the burning temperature is usually 50 to 1000° C., preferably100 to 1000° C., more preferably 150 to 450° C. The burning time isgenerally 5 minutes or more, preferably 10 minutes or more. The burningatmosphere may be generally the ambient atmosphere (in the air), but anatmosphere with a higher content of oxygen and/or a higher partialpressure of water vapor may also be used in order to promote oxidationof the polysilazane.

In the pretreatment step for burning this polysilazane film, thepatterned polysilazane film is subjected to exposure and moisteningtreatment, whereby a silica type ceramic film with a low dielectricconstant excellent in heat resistance, abrasion resistance, corrosionresistance, insulating properties and transparency and suitable as e.g.an inter-layer dielectric can be easily formed. That is, as theradiation sensitive polysilazane composition comprising the polysilazaneand the photo acid generator is a positive working composition, theradiation sensitive polysilazane coating film remaining as a patterncontains the photo acid generator in the initial amount. Accordingly,when exposure and moistening treatment of the radiation sensitivepolysilazane coating film are conducted in the pretreatment step forburning, an acid is formed in the coating film in the same mechanism asin patterning of the radiation sensitive polysilazane coating film asdescribed above, and by the catalytic action of this acid, Si—N linkagesin the polysilazane are cleaved, and the conversion thereof into Si—OHis promoted by the moistening treatment. The polysilazane film thusconverted into Si—OH is easily converted by burning into SiOSi to give asilica type ceramic film having no or few SiNH linkages in the filmafter burning.

Exposure as the pretreatment step for burning of the radiation sensitivepolysilazane coating film may be conducted in an analogous manner topattern exposure of the radiation sensitive polysilazane coating film.That is, as a light source used for exposure, any one such as ahigh-pressure mercury lamp, low-pressure mercury lamp, metal halidelamp, xenon lamp, excimer laser, X-rays, electron rays or the like canbe used depending on the radiation sensitive range of the radiationsensitive polysilazane composition. In exposure in the pretreatment stepfor burning, it is preferable that the substrate is wholly exposed onceto light, but if necessary, only the patterned portion or a part of thesubstrate may be exposed to light once or several times. The intensityof light exposed is varied depending on the light source, the thicknessof the film, and the sensitivity of the radiation sensitive compositionused, but it is usually 0.05 mJ/cm² or more, desirably 0.1 mJ/cm² ormore. There is no particular upper limit of the intensity, but 10000mJ/cm² or less is practical. The atmosphere in exposure may be theambient atmosphere (in the air) or a nitrogen atmosphere as is the casewith exposure for patterning, but an atmosphere enriched in oxygen mayalso be used in order to promote decomposition of the polysilazane.

Further, the moistening treatment as the pretreatment step for burningmay be also conducted by bringing the light-exposed radiation sensitivepolysilazane film into contact with a water vapor-containing gas in thesame manner as in the moistening treatment after patternwise exposure ofthe radiation polysilazane film. In the moistening treatment as thepretreatment step for burning of the radiation sensitive polysilazanefilm of this invention, when the moistening treatment of the radiationsensitive polysilazane film in exposure in the pretreatment for burningis conducted by moisture in the atmosphere, the moistening treatment atthe time of exposure can also serve as the moistening treatment in thepretreatment step for burning. From the viewpoint of shortening thetreatment time, however, the moistening treatment of the film isconducted preferably with a highly humid gas containing a larger amountof water than in the gas used in exposure. When the film is subjected tomoistening treatment in a heated state, conversion of the polysilazaneinto SiOH is promoted as same as the case of the moistening treatment ofthe radiation sensitive polysilazane film after subjected to patternwiseexposure. Accordingly, the method of moistening treatment is preferablya method wherein the substrate having the light-exposed radiationsensitive polysilazane film is placed on a heating plate, and thesubstrate is contacted in a heated state with a highly humid gas.

The burning temperature, burning time and burning atmosphere for theradiation sensitive polysilazane coating film after subjected tomoistening treatment maybe a range or conditions similar to those of thefilm not subjected to moistening treatment.

This invention has been described in detail by reference to a modewherein a patterned coating film of the radiation sensitive polysilazaneis formed and then this patterned coating film of the radiationsensitive polysilazane is burned. But the coating film of the radiationsensitive polysilazane may be burned directly without subjecting it topatterning, thus permitting the whole area of the coating film to beconverted to silica type ceramic film. In this case too, the conditionsof exposure and moistening treatment as the pretreatment step forburning may be similar to those for burning the patterned coating filmof the radiation sensitive polysilazane.

By the pretreatment and subsequent burning as described above, a silicatype ceramic film characterized by a dielectric constant of 5 or less,sometimes a dielectric constant of 3.3 or less and a resistivity of atleast 10¹³ Ω·cm can be obtained.

EXAMPLES

Hereinafter, this invention is described in more detail by reference tothe Examples, which however are not intended to limit the scope of thisinvention.

Reference Example Preparation of Modified Poly(Sil Sesquiazane)

A gas inlet, a mechanical stirrer, a Dewar condenser were attached to afour-necked flask. The atmosphere in the reaction flask was replaced bydeoxygenated dry nitrogen. Starting materials CH₃SiCl₃ and (CH₃)₂SiCl₂and/or (CH₃)₃SiCl (about 50 g in total) were charged into the flask in apredetermined molar ratio, and mixed. Then, degassed dry pyridine wasintroduced thereto such that the concentration of the starting materialswas reduced to about 10% by weight, and the mixture was cooled on ice.While the mixture of the starting materials was stirred, a mixture ofammonia (NH₃) and a nitrogen gas was introduced to it until the reactionwas completed

After the reaction was completed, the solid product was separated bycentrifugation and then removed by filtration. By removing the solventunder reduced pressure from the filtrate, a modified poly(silsesquiazane) was obtained.

The ratio of the constituent unit —[Si(CH₃)₂NH]— to the constituent unit—[Si(CH₃)₃(NH)_(0.5)]— in the modified poly(sil sesquiazane) can bedetermined by its Si-NMR spectrum. Further, the constitution of themodified poly(sil sesquiazane) can be roughly known by characteristicpeaks attributable to various bonds in its infrared (IR) absorptionspectrum. For example, an IR spectrum of the modified poly(silsesquiazane) containing 20 mol-% of —[Si(CH₃)₂NH]— as the otherconstituent unit is shown in FIG. 3. From these measurement results, itwas confirmed that the ratio of the various constituent units in themodified poly(sil sesquiazane) almost reflects the molar ratio of thecorresponding starting materials.

Example 1 and Comparative Example 1

According to the procedure described in the Reference Example, amodified poly(sil sesquiazane) containing —[SiCH₃(NH)_(1.5)]— as thebasic constituent unit and about 10 mol-% of —[Si(CH₃)₂NH]— wasprepared. To this modified poly(sil sesquiazane), a sulfoxime derivative[4-methoxy-α-((((4-methoxyphenyl)sulfonyl)oxy)imino)benzeneacetonitrile] represented by the formula (1) below was added as a photoacid generator in an amount of 5% by weight relative to the polymer, anda coumarin dye represented by the formula (2) below was added as asensitizer in an amount of 10% by weight. The whole of the mixture wasdiluted with xylene such that the polymer concentration was adjusted to15% by weight.

This solution was divided into two solutions, to one of which2-nitroaniline was added in an amount of 2% by weight relative to themodified poly(sil sesquiazane). The other solution to which2-nitroaniline was not added was used as Comparative Example 1.

Each solution was spin-coated on a silicon substrate at 2000 rpm(coating thickness: 0.4 μm). This coating film was exposed through amask having a 0.5 μm isolated pattern with 40 mJ/cm² irradiation amountby a KrF excimer laser exposure device. Then, the coating film wasdeveloped with 2.38 weight-% aqueous TMAH (tetramethylammoniumhydroxide).

The resultant silicon substrate having the patterned film thereon wascut, and the cleaved surface was observed in the direction of thesection under an electron microscope (SEM) to determine the angle ofinclination.

Example 2

The same procedure as in Example 1 was repeated except that in place of2-nitroaniline, 2-nitropropane was added in an amount of 1% by weightrelative to the modified poly(sil sesquiazane).

Example 3

The same procedure as in Example 1 was repeated except that in place of2-nitroaniline, propylene carbonate was added in an amount of 5% byweight relative to the modified poly(sil sesquiazane).

Example 4

The same procedure as in Example 1 was repeated except that in place of2-nitroaniline, a water-soluble acrylic polymer (acrylic polymer “AlonA-20P” (trade name) produced by Toagosei Chemical Industry Co., Ltd.)was added in an amount of 10% by weight relative to the modifiedpoly(sil sesquiazane).

[Comparison of the Angles of Inclination]

The inclination angles of the patterned films obtained in Examples 1 to4 and Comparative Example 1 are as follows:

Example Angle of inclination (degrees) Example 1 90 Example 2 90 Example3 90 Example 4 90 Comparative Example 1 70[Comparison of the Characteristics of the Burned Films]

Then, the pattern films obtained in Examples 1 to 4 and ComparativeExample 1 were burned under the following conditions. The burned filmswere measured in the following manner for their dielectric constant andfilm hardness and evaluated for their usefulness as inter-layerdielectric.

Burning Conditions

Each patterned film was pre-heated on a hot plate at 150° C. for 1minute and then placed in a burning oven at 400° C. for 30 minutes.

Method of Measuring Dielectric Constant

An aluminum specimen having an area of 1 mm² was formed on an upper partof the burned film, to prepare an upper electrode. An alloy layer wasformed on the silicon substrate to form a lower electrode, and a MOScapacitor was constituted as a whole. Capacitance of the MOS capacitor(C-V character) was measured with an HP4192A impedance analyzer (made byHewlett-Packard Co.) by applying bias voltage across the capacitor, andfrom this character, the dielectric constant was calculated.

Measurement of Hardness

Film hardness of burned films was measured by Nano Indenter XP producedby MTS Systems Co.

Comparison of Characteristics

The measurement results are as follows:

Dielectric Hardness Example Constant (GPa) Example 1 to 2.6 1.0 Example2 to 2.6 1.0 Example 3 to 2.6 1.0 Example 4 to 2.2 0.7 ComparativeExample 1 to 2.6 1.0

The results of dielectric constant and hardness indicate that the burnedfilms obtained according to this invention have useful characteristicsas an inter-layer dielectric.

Example 5

According to the procedure described in the Reference Example, amodified poly(sil sesquiazane) comprising —[SiCH₃(NH)_(1.5)]— as a basicconstituent unit and 5mol-% —[Si(CH₃)₃(NH)_(0.5)]— was prepared. To thismodified poly(sil sesquiazane), a triazine derivative represented by theformula:

was added as a photo acid generator in an amount of 1% by weight, andthis mixture was diluted with propylene glycol monomethyl ether acetate(PGMEA) such that the total solid content was adjusted to 10% by weight,to prepare a radiation sensitive polysilazane composition. Thisradiation sensitive polysilazane composition was spin-coated at 1000 rpmonto a silicon substrate, and then pre-baked at 90° C. for 90 seconds toform a coating film of 0.4 μm in thickness. The substrate having thiscoating film of the radiation sensitive polysilazane composition wasexposed through a mask having 1:1 line and space patterns having variousline widths to varying variation in a step of 15 mJ/cm² from 10 mJ/cm²to 1000 mJ/cm² by a KrF excimer laser exposure device. Then, the coatingfilm was subjected to moistening treatment at 25° C. at 60% RH for 5minutes, and the substrate was developed with 2.38 weight-% aqueous TMAHfor 1 minute, and then the substrate was rinsed with pure water. Theresultant pattern was observed under SEM. The amount of irradiation bywhich the exposed part of the coating film could be completely removedwas defined as sensitivity, and the results shown in Table 1 wereobtained.

Comparative Example 2

The same procedure as in Example 5 was conducted except that themoistening treatment conditions were those described in Table 1, and theresults shown in Table 1 were obtained.

TABLE 1 Moistening treatment conditions Treatment Temperature Humiditytime Sensitivity (° C.) (% RH) (min) (mJ/cm²) Example 5 25 60 5 70Comparative 25 35 0 >1000 Example 2

As can be seen from the results in Table 1 above, the sensitivity of theradiation sensitive polysilazane composition is improved by increasingthe humidity in the atmosphere at the time of treatment, whereby thetreatment time can be shortened.

Examples 6 to 8

According to the procedure described in the Reference Example, amodified poly(sil sesquiazane) comprising —[SiCH₃(NH)_(1.5)]— as a basicconstituent unit and 10 mol-% of —[Si(CH₃)₂NH]— was prepared. To thismodified poly(sil sesquiazane), a sulfoxime derivative represented bythe formula:

was added as a photo acid generator in an amount of 5% by weight, and acoumarin derivative represented by the formula:

was added as a sensitizer in an amount of 10% by weight. The mixture wasdiluted with butyl acetate such that the total solid content was reducedto 10% by weight to prepare a radiation sensitive polysilazanecomposition. This radiation sensitive polysilazane composition wasspin-coated at 1000 rpm onto a silicon substrate, and then spin-dried toform a coating film of 0.4 μm in thickness. Then, the substrates wereexposed through a mask having 1:1 line and space patterns having variousline widths with an irradiation amount of 0.1 mJ/cm² step from 0.1mJ/cm² to 1 mJ/cm², an irradiation amount of 1 mJ/cm² step from 1 mJ/cm²to 10 mJ/cm², an irradiation amount of 10 mJ/cm² step from 10 mJ/cm² to100 mJ/cm², and an irradiation amount of 100 mJ/cm² step from 100 mJ/cm²to 1000 mJ/cm² by an i-ray exposure device respectively. The exposedsubstrate was placed on a heating plate in a moistening treatmentapparatus, and then treated under the moistening treatment conditionsdescribed in Table 2, developed and rinsed in the same manner as inExample 5, to give the sensitivity shown in Table 2.

Comparative Example 3

The same procedure as in Example 6 was conducted except that themoistening treatment conditions were shown in Table 2, and the resultsshown in Table 2 were obtained.

TABLE 2 Moistening treatment conditions Treatment Temperature Humiditytime Sensitivity (° C.) (% RH) (min) (mJ/cm²) Example 6 25 60 5 70Example 7 50 50 3 10 Example 8 90 50 1 0.2 Comparative 25 35 0 >1000Example 3

As can be seen from the results shown in Tables 1 and 2, the treatmenttime can be reduced by heating the substrate during the treatment.Further even if the treatment is conducted at the same humidity, thesensitivity is improved by the moistening treatment under heatingconditions, whereby the treatment time can be further reduced.

Examples 9 to 11

According to the procedure described in the Reference Example, amodified poly(sil sesquiazane) comprising —[SiCH₃(NH)_(1.5)]— as a basicconstituent unit and 10 mol-% of —[Si(Ph)₂NH]— (Ph: phenyl group) wasprepared. To this modified poly(sil sesquiazane), a peroxide representedby the formula:

was added as a photo acid generator in an amount of 1% by weight. Thismixture was diluted with PGMEA such that the total solid content wasreduced to 30% by weight, to prepare a radiation sensitive polysilazanecomposition. This radiation sensitive polysilazane composition wasspin-coated at 3000 rpm onto a silicon substrate, and then pre-baked at60° C. for 60 seconds to form a coating film of 0.8 μm in thickness. Thesubstrate having this coating film of the radiation sensitivepolysilazane composition was printed by exposing it to an irradiationamount of 80 μC/cm² by an electron ray exposure device as the exposuredevice through a mask having 1:1 line and space patterns having variousline widths. Then, the substrate was treated under the moisteningtreatment conditions shown in Table 3, and then developed for 1 minutewith 2.38 weight-% aqueous TMAH, and then the substrate was rinsed withpure water, and the resultant pattern was observed under SEM, to confirmthe destruction of the pattern. The line width of the minimum patternthat was not destructed is shown in Table 3.

TABLE 3 Moistening treatment conditions Minimum Treatment pattern notTemperature Humidity time destructed (° C.) (% RH) (min) (μm) Example 925 50 10  0.5 Example 10 30 50 3 0.3 Example 11 70 50 3 0.075

As can be seen from the results shown in Table 3, the destruction of thepattern hardly occurs by development treatment under heating andmoistening conditions, that is, the adhesion of the pattern to thesubstrate is improved.

Example 12

According to the procedure described in the Reference Example, amodified poly(sil sesquiazane) comprising —[SiCH₃(NH)_(1.5)]— as a basicconstituent unit, 5 mol-% of —[Si(CH₃)₃(NH)_(0.5)]— and 1 mol-% of—[Si(CH₃)₂NH]— was prepared. To this modified poly(sil sesquiazane), atriazine derivative represented by the formula:

was added as a photo acid generator in an amount of 1% by weight, andthis mixture was diluted with propylene glycol monomethyl ether acetate(PGMEA) such that the total solid content was reduced to 10% by weight,to prepare a radiation sensitive polysilazane composition. Thisradiation sensitive polysilazane composition was spin-coated at 1000 rpmonto a silicon substrate, and then pre-baked at 90° C. for 90 seconds toform a coating film of 0.4 μm in thickness. Then, the coating film waswholly exposed once with an irradiation amount of 100 mJ/cm² by alow-pressure mercury lamp. The coating film was subjected to moisteningtreatment at 25° C. at 50% RH for 5 minutes and burned at 400° C. for 30minutes. The resulting burned film was examined for its dielectricconstant and for the presence of remaining Si—NH linkages. The resultsare shown in Table 4.

The presence of remaining Si—NH linkages was determined by taking an IRabsorption spectrum of the burned film with an IR spectrophotometer. TheIR absorption spectrum of the burned film is shown in FIG. 4.

Comparative Example 4

The same procedure as in Example 12 was conducted except that the whollyexposure and the moistening treatment were not conducted, and theresults shown in Table 4 were obtained. An IR absorption spectrum of theburned film formed in Comparative Example 4 is shown in FIG. 5.

TABLE 4 Comparative Example 12 Example 4 Pretreatment condition forLow-pressure Not treated burning mercury lamp (wholly exposure) 100mJ/cm² Pretreatment condition for 25° C. at 50% RH Not treated burningfor 5 minutes (Moistening treatment) Burning conditions 400° C. for 30400° C. for 30 minutes minutes Dielectric constant 2.7 3.8 RemainingSi—NH Absent present (IR spectrometry) (see FIG. 4) (see FIG. 5)

As can be seen from the results shown in Table 4, the burned film havinga low dielectric constant and free of Si—NH linkages in the film can beformed by subjecting the radiation sensitive polysilazane coating filmbefore burning to exposure and moistening treatment.

Examples 13 to 15

According to the procedure described in the Reference Example, amodified poly(sil sesquiazane) comprising —[SiCH₃(NH)_(1.5)]— as a basicconstituent unit and 20 mol-% of —[Si(CH₃)₂NH]— was prepared. To thismodified poly(sil sesquiazane), a sulfoxime derivative represented bythe formula:

was added as a photo acid generator in an amount of 1% by weight, andthis mixture was diluted with PGMEA such that the total solid contentwas reduced to 10% by weight to prepare a radiation sensitivepolysilazane composition. This radiation sensitive polysilazanecomposition was spin-coated at 1000 rpm onto a silicon substrate anddried by spin-drying, to form a coating film of 0.4 μm in thickness.Then, the coating film was wholly exposed once to an irradiation amountof 100 mJ/cm² by a high-pressure mercury lamp. The exposed substrate wasplaced on a heating plate in a moistening treatment apparatus, thentreated under the moistening conditions shown in Table 5 and burned at400° C. for 30 minutes. The resulting burned film was examined in thesame manner as in Example 12 for its dielectric constant and for thepresence of remaining Si—NH linkages. The results are shown in Table 5.

Comparative Example 5

The same procedure as in Example 13 was conducted except that themoistening treatment conditions were those shown in Table 5, and theresults in Table 5 were obtained.

TABLE 5 Comparative Example 13 Example 14 Example 15 Example 5Pretreatment low- low- low- Not treated condition for pressure pressurepressure burning mercury mercury mercury (wholly lamp lamp lampExposure) 100 mJ/cm² 100 mJ/cm² 100 mJ/cm² Pretreatment 25° C. 30° C.70° C. Not treated condition for at 50% RH at 80% RH at 50% RH burningfor 1 minute for 1 minute for 1 minute (Moistening treatment) Burning400° C. for 400° C. for 400° C. for 400° C. for conditions 30 minutes 30minutes 30 minutes 30 minutes Dielectric 3.3 2.7 2.7 3.8 constantRemaining Present Absent Absent present Si—NH (IR spectrometry)

As can be seen from the results shown in Table 5, the burned film havinga low dielectric constant and free of Si—NH linkages in the film can beformed by the moistening treatment at high humidity or by the moisteningtreatment under heating, as opposed to the moistening treatment at lowhumidity and at low temperature. As can also be seen from this result,the process time can be shortened by the moistening treatment at highhumidity under heating.

EFFECT OF THE INVENTION

As illustrated above, the following effects are obtained according tothe present invention.

(1) The treatment for promoting decomposition of the polysilazane afterexposure of the radiation sensitive polysilazane composition isconducted using a vapor water-containing gas, whereby the moisteningtreatment can be conducted in a short time. Further, by increasing thehumidity of the gas, the sensitivity can be improved and the treatmenttime can be shortened. Further, by the moistening treatment of thecoating film on a substrate in a heated state, the treatment underhigher humidity conditions is feasible, to achieve the effects offurther improvements in sensitivity, an increase in the rate ofprocessing, and improvements in the adhesion between the substrate andthe radiation sensitive polysilazane composition.

(2) When the radiation sensitive polysilazane coating film which waspatterned or not patterned is burned, the radiation sensitivepolysilazane coating film is subjected to exposure to light andmoistening treatment in the pretreatment step before burning, whereby asilica type ceramic film with a low dielectric constant excellent ininsulating properties, heat resistance, abrasion resistance, corrosionresistance and transparency and free of Si—N linkages derived from thepolysilazane in the burned film can be formed by heating at lowtemperature in a short time. Further, a highly humid gas is used in themoistening treatment as the pretreatment step for burning, or theradiation sensitive polysilazane coating film is heated duringmoistening treatment, whereby shorter time conversion of thepolysilazane in the film into SiOH proceeds, and the treatment time canbe reduced as a whole.

(3) By adding a water-soluble compound as a shape stabilizer to theradiation sensitive polysilazane composition comprising a specificmodified poly(sil sesquiazane), the difference in sensitivity of theradiation sensitive composition in the direction of film thickness canbe solved, whereby the side wall of the pattern section in the patternformed by exposure can be made steep to improve pattern resolution.Further, the resultant insulating film can serve as a finely patternedfilm having a low dielectric constant, excellent in mechanicalcharacteristics such as abrasion resistance and excellent as aninter-layer dielectric.

(4) The patterned polysilazane film obtained according to the method offorming a pattern or the novel radiation sensitive polysilazanecomposition of the present invention can be used directly as a resistsuch as etching resist or as a coating constituting displays, and thefilm can also be converted into a silica type ceramic film which can beused as an inter-layer dielectric or the like in semiconductor devicesor LCD.

1. A method of forming a patterned polysilazane film by exposing andthen developing a coating film of a radiation sensitive polysilazanecomposition, wherein the exposed radiation sensitive polysilazanecoating film is contacted with a gas containing water vapor withrelative humidity to the temperature of the substrate of from 35% RH to90% RH and then developed.
 2. The method of forming a patternedpolysilazane film according to claim 1, wherein the radiation sensitivepolysilazane coating film is heated at the time of the contact with agas containing water vapor.
 3. A method of burning a radiation sensitivepolysilazane coating film, wherein the steps of exposing with light andmoistening by contacting with a gas containing water vapor with relativehumidity to the temperature of the substrate of from 35% RH to 90% RHthe radiation sensitive polysilazane coating film are provided aspretreatment steps for burning and then said exposed and moistenedradiation sensitive polysilazane coating film is burned.
 4. The methodof burning a radiation sensitive polysilazane coating film according toclaim 3, wherein the radiation sensitive polysilazane coating film hasbeen patterned.
 5. The method of burning a radiation sensitivepolysilazane coating film according to claim 3, wherein the radiationsensitive polysilazane coating film is heated at the time of themoistening treatment.
 6. A radiation sensitive polysilazane compositioncomprising a modified poly(sil sesquiazane) having a number averagemolecular weight of 100 to 100,000 and containing a basic constituentunit represented by the general formula: —[SiR⁶(NR⁷)_(1.5)]— and otherconstituent units represented by the general formula: —[SiR⁶ ₂NR⁷]—and/or —[SiR⁶ ₃(NR⁷)_(0.5)]— (in the aforementioned formulae, R⁶independently represents a C₁₋₃ alkyl group or a substituted orunsubstituted phenyl group and R⁷ independently represents a hydrogenatom, a C₁₋₃ alkyl group or a substituted or unsubstituted phenyl group)in a ratio of 0.1 to 100 mol-% to said basic constituent unit, a photoacid generator, and a water-soluble compound as a shape stabilizer. 7.The radiation sensitive polysilazane composition according to claim 6,wherein the photo acid generator is ones selected from the groupconsisting of a sulfoxime type compound and a triazine type compound. 8.The radiation sensitive polysilazane composition according to claim 6,which further comprises a dissolution inhibitor.
 9. The radiationsensitive polysilazane composition according to claim 8, wherein thedissolution inhibitor is ones selected from the group consisting oft-butoxycarbonylated catechol, t-butoxycarbonylated hydroquinone,t-butyl ester of benzophenone-4,4′-dicarboxylic acid, and t-butyl esterof 4,4′-oxydibenzoic acid, and is contained in an amount of 0.1 to 40%by weight relative to the radiation sensitive polysilazane composition.10. The radiation sensitive polysilazane composition according to ofclaim 6, wherein the water-soluble compound is a compound with a nitrogroup.
 11. The radiation sensitive polysilazane composition according toclaim 6, wherein the water-soluble compound is a compound containing acarbonate.
 12. The radiation sensitive polysilazane compositionaccording to claim 6, which further comprises a sensitizing dye.
 13. Theradiation sensitive polysilazane composition according to claim 6,wherein the radiation sensitive polysilazane composition is used as aninter-layer dielectric.
 14. A method of forming a patterned inter-layerdielectric, which comprises forming a coating film of a radiationsensitive polysilazane composition comprising a modified poly(silsesquiazane) having a number average molecular weight of 100 to 100,000and containing a basic constituent unit represented by the generalformula: —[SiR⁶(NR⁷)_(1.5)]— and other constituent units represented bythe general formula: —[SiR⁶ ₂NR⁷]— and/or —[SiR⁶ ₃(NR⁷)_(0.5)]— (in theaforementioned formulae, R⁶ independently represents a C₁₋₃ alkyl groupor a substituted or unsubstituted phenyl group and R⁷ independentlyrepresents a hydrogen atom, a C₁₋₃ alkyl group or a substituted orunsubstituted phenyl group) in a ratio of 0.1 to 100 mol-% to said basicconstituent unit, a photo acid generator, and a water-soluble compoundas a shape stabilizer, patternwise irradiating the coating film,dissolving and removing the irradiated part of the coating film, andleaving the residual patterned coating film in the ambient atmosphere orburning the coating film.